Every so often, a new portfolio item’s thumbnail does not accept the grayscale overlay I’ve placed using CSS. The current issue can be seen in the first row of http://kirindesigngr.com/portfolio There is a broken jpeg symbol over the thumbnail in Chrome as if something is wrong.

I’ve already regenerated the thumbnail, changed the file name and uploaded three versions, and created a separate portfolio item with the same image in case something broke during the initial creation of the current item.

This issue only occurs one in five uploads, but is extremely aggravating when it does, as nothing rational will fix it.

I tried all of that. First, I disabled W3 Total Cache and reloaded the page. Then I disabled all my plugins and uploaded a .jpg version of the image. Still came out the same. I left the .jpg version up even though the thumbnail position is wrong to demonstrate the point.

Please post the list of plugins that you have on your end. Check if the greyscale version of the image is present on the wp-content/uploads/2014/03 folder. You can also fix it using CSS. Add this on Quick CSS or custom.css: